The present invention relates generally to the field of engine control systems which sense various engine operating parameters and develop engine control signals. More particularly, the present invention relates to an improved engine control system for providing engine control in accordance with a torque polarity engine control signal which is indicative of actual sensed engine fuel consumption and expected engine fuel consumption.
Engine control systems are known which have recognized that during engine deceleration the engine momentum may result in the engine consuming less than the amount of fuel which is normally needed to maintain a predetermined engine speed. After the deceleration condition, then the engine will revert to consuming an expected amount of fuel in order to maintain the resultant final engine speed. During such an engine deceleration, some engine control systems have provided for either increasing or at least controlling the amount of air in the engine fuel mixture so that during deceleration an excessive amount of fuel will not be consumed. Some of these engine control systems provide additional air to the fuel mixture during deceleration in accordance with the difference between actual sensed engine manifold pressure and a fixed expected value of engine manifold pressure which is stored in a memory circuit in the engine control system.
Engine control systems such as those described above have improved engine performance by insuring the consumption of a more proper air-fuel mixture during deceleration. However, typically these systems have not produced optimum results since the amount of reduction of the fuel mixture (enleanment) is a function of actual sensed manifold pressure versus one or more predetermined fixed stored reference values of expected manifold pressure. Thus under various different engine operating conditions relating to load, engine speed, current engine efficiency and/or other engine operating parameters, an erroneous reference value of the expected manifold pressure may be utilized. In other words, by utilizing a fixed expected reference manifold pressure, the previous engine control systems, even though some of them may compensate this reference level for engine speed, are not sufficiently representative of actual engine performance which is a function of engine load, the current operating efficiency of the engine (which can be affected by when the engine was last tuned up), and many other factors.